Variables associated with cortical motor mapping thresholds: A retrospective data review with a unique case of interlimb motor facilitation.

Introduction: Intraoperative neuromonitoring (IONM) is crucial to preserve eloquent neurological functions during brain tumor resections. We observed a rare interlimb cortical motor facilitation phenomenon in a patient with recurrent high-grade glioma undergoing craniotomy for tumor resection; the patient's upper arm motor evoked potentials (MEPs) increased in amplitude significantly (up to 44.52 times larger, p < 0.001) following stimulation of the ipsilateral posterior tibial nerve at 2.79 Hz. With the facilitation effect, the cortical MEP stimulation threshold was reduced by 6 mA to maintain appropriate continuous motor monitoring. It likely has the benefit of reducing the occurrence of stimulation-induced seizures and other adverse events associated with excessive stimulation. Methods: We conducted a retrospective data review including 120 patients who underwent brain tumor resection with IONM at our center from 2018 to 2022. A broad range of variables collected pre-and intraoperatively were reviewed. The review aimed to determine: (1) whether we overlooked this facilitation phenomenon in the past, (2) whether this unique finding is related to any specific demographic information, clinical presentation, stimulation parameter (s) or anesthesia management, and (3) whether it is necessary to develop new techniques (such as facilitation methods) to reduce cortical stimulation intensity during intraoperative functional mapping. Results: There is no evidence suggesting that clinical presentation, stimulation configuration, or intraoperative anesthesia management of the patient with the facilitation effect were significantly different from our general patient cohort. Even though we did not identify the same facilitation effect in any of these patients, we were able to determine that stimulation thresholds for motor mapping are significantly associated with the location of stimulation (p = 0.003) and the burst suppression ratio (BSR) (p < 0.001). Stimulation-induced seizures, although infrequent (4.05%), could occur unexpectedly even when the BSR was 70%. Discussion: We postulated that functional reorganization and neuronal hyperexcitability induced by glioma progression and repeated surgeries were probable underlying mechanisms of the interlimb facilitation phenomenon. Our retrospective review also provided a practical guide to cortical motor mapping in brain tumor patients under general anesthesia. We also underscored the need for developing new techniques to reduce the stimulation intensity and, hence, seizure occurrence.

Intraoperative neurophysiological monitoring of T9-T10 fracture in a patient with morbid obesity and ankylosing spondylitis: A case report with literature review.

INTRODUCTION: As the prevalence of obesity continues to rise, there is a growing need to identify practices that protect overweight patients from injury during spine surgery. Intraoperative neurophysiological monitoring (IONM) has been recommended for complex spine surgery, but its use in obese and morbidly obese patients is understudied. CASE REPORT: This case report describes a patient with morbid obesity and ankylosing spondylitis who was treated for a T9-T10 3-column fracture with a planned, minimally invasive approach. Forty minutes after positioning the patient to prone, the IONM team identified a positive change in the patient's motor responses in the bilateral lower extremities and alerted the surgical team in a timely manner. It turned out that the pressure exerted by gravity on the patient's large pannus resulted in further dislocation of the fracture and narrowing of the spinal canal. The surgical team acknowledged the serious risk of spinal cord compression and, hence, immediately changed the surgical plan to an urgent, open approach for decompression and reduction of the fracture. The patient's lower extremities' motor responses improved after decompression. The patient was ambulatory on post-operative day 2 and pain-free at six-weeks with no other neurologic symptoms. SIGNIFICANCE: The use of IONM in this planned minimally invasive spine surgery for a patient with morbid obesity prevented potentially serious iatrogenic injury. The authors include a literature review that situates this case study in the existing literature and highlights a gap in current knowledge. There are few studies that have examined the use of IONM during spine surgery for morbidly obese patients. More research is needed to elucidate best practices for the use of IONM in spine surgery for morbidly obese patients.

Investigating social cognition in epilepsy using a naturalistic task.

OBJECTIVE: The primary objective for this study was to assess social cognition in patients with focal epilepsy using a naturalistic task, which accurately models complex real-world social interaction. METHODS: We conducted an observational study of social cognition in 43 patients with focal epilepsy and in 22 controls. Patients and controls completed The Awareness of Social Inference Test, which measures both basic and advanced social cognition in a realistic video-based format. Patient and controls also completed standard measures of cognitive functioning and measures of depression. RESULTS: Compared to controls, we found that patients with epilepsy (PWEs) had no difficulty identifying positively valenced emotional states (happiness) yet had difficulty identifying most negatively valenced emotional states (anger, fear, and disgust). In addition, PWEs were able to identify sincere exchanges correctly but could not identify sarcastic and insincere exchanges. We found that basic social cognition significantly correlated with standard generalized cognitive measures, whereas advanced social cognition did not. Finally, age at onset had significant impact on social cognition, whereas other epilepsy characteristics did not. SIGNIFICANCE: PWEs have deficits in social cognition when measured using a naturalistic video-based task. Advanced social cognition may be an independent cognitive domain in PWEs that is not adequately measured using standard psychometric instruments. Problems with social cognition may arise as a consequence of epilepsy during the periods of robust social development in childhood and adolescence.

Safe use of subdermal needles for intraoperative monitoring with MRI.

OBJECTIVE: The purpose of this study was to develop safe, site-specific procedures for placing and leaving subdermal needle leads for intraoperative monitoring (IOM) during intraoperative MRI procedures. METHODS: The authors tested a variety of standard subdermal needle electrodes designed and FDA-approved for IOM in the conventional operating room. Testing was used to determine the conditions necessary to avoid thermal injury and significant image artifacts with minimal disruption of IOM and MRI procedures. Phantom testing was performed with a fiber optic (lead) temperature monitoring system and was followed by testing of leads placed in a healthy volunteer. The volunteer testing used electrode placements typical of standard IOM cases, together with radiofrequency (RF) coil placement and imaging sequences routinely employed for these case types. Lead length was investigated to assess heating effects for electrodes placed within the RF coil. RESULTS: The authors found that conventional stainless steel (SS) and platinum/iridium (Pt/Ir) subdermal needles can be used safely without significant heating when placed outside the RF coil, and this accounts for the majority or entirety of electrode placements. When placed within the RF coil, Pt/Ir leads produced minimal image artifacts, while SS leads produced potentially significant artifacts. In phantom testing, significant heating was demonstrated in both SS and Pt/Ir leads placed within the RF coil, but only during high-resolution T2-weighted scanning. This problem was largely, but not completely, eliminated when leads were shortened to 25 cm. Human testing was unremarkable except for nonpainful heating detected in a few electrodes during thin-slice (1.5 mm) FLAIR scanning. Transient irritation (skin reddening along the needle tract) was noted at 2 of the electrodes with detectable heating. CONCLUSIONS: The authors were satisfied with the safety of their site-specific procedures and have begun with off-label use (following institutional review board approval and obtaining patient informed consent) of tested monitoring leads in cases that combine IOM and MRI. The authors recommend that all facilities perform their own site-specific testing of monitoring leads before proceeding with their routine use.

Quality improvement opportunities in caring for patients with nonepileptic seizures.

Background. Patients with nonepileptic seizures (NES) are challenging to treat for myriad reasons. Often patients may be misdiagnosed with having epilepsy and then may suffer unintended consequences of treatment side effects with antiepileptic medication. In addition, patients may be maligned by health care providers due to a lack of ownership by both psychiatrists and neurologists and a dearth of dedicated professionals who are able to effectively treat and reduce severity and frequency of symptoms. Aims of Case Report. Many psychiatrists and neurologists are unaware of the extent of the barriers to care faced by patients with NES (PWNES) and the degree of perception of maltreatment or lack of therapeutic alliance at various stages of their care, including medical workup, video-EEG monitoring, and follow-up plans. We present the case of a patient with NES who experienced numerous barriers as well as incoordination to her care despite being offered a breadth of resources and discuss the quality improvement opportunities that may exist to improve care of patients with NES. Conclusion. No known literature has documented the extensive barriers to care of PWNES in parallel to quality improvement opportunities for improving their care. We endeavor to contribute to the overall formulation and development of a clinical care pathway for PWNES.

Reducing severity of comorbid psychiatric symptoms in an epilepsy clinic using a colocation model: results of a pilot intervention.

RATIONALE: Patients with epilepsy (PWEs) and patients with nonepileptic seizures (PWNESs) constitute particularly vulnerable patient populations and have high rates of psychiatric comorbidities. This potentially decreases quality of life and increases health-care utilization and expenditures. However, lack of access to care or concern of stigma may preclude referral to outpatient psychiatric clinics. Furthermore, the optimal treatment for NESs includes longitudinal psychiatric management. No published literature has assessed the impact of colocated psychiatric services within outpatient epilepsy clinics. We, therefore, evaluated the colocation of psychiatric services within a level 4 epilepsy center. METHODS: From July 2013 to June 2014, we piloted an intervention to colocate a psychiatrist in the Dartmouth-Hitchcock Epilepsy Center outpatient clinic one afternoon a week (0.1 FTE) to provide medication management and time-limited structural psychotherapeutic interventions to all patients who scored greater than 15 on the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) and who agreed to referral. Psychiatric symptom severity was assessed at baseline and follow-up visits using validated scales including NDDI-E, Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and cognitive subscale items from Quality of Life in Epilepsy-31 (QOLIE-31) scores. RESULTS: Forty-three patients (18 males; 25 females) were referred to the clinic over a one-year interval; 27 (64.3%) were seen in follow-up with a median of 3 follow-up visits (range: 1 to 7). Thirty-seven percent of the patients had NESs exclusive of epilepsy, and 11% of the patients had dual diagnosis of epilepsy and NESs. Psychiatric symptom severity decreased in 84% of the patients, with PHQ-9 and GAD-7 scores improving significantly from baseline (4.6±0.4 SD improvement in PHQ-9 and 4.0±0.4 SD improvement in GAD-7, p-values<0.001). Cognitive subitem scores for NDDI-E and QOLIE-31 at their most recent visit were significantly improved compared with nadir scores (3.3±0.6 SD improvement in NDDI-E and 1.5±0.2 SD improvement in QOLIE-31, p-values<0.001). These results are, moreover, clinically significant-defined as improvement by 4-5 points on PHQ-9 and GAD-7 instruments-and are correlated with overall improvement as measured by NDDI-E and cognitive subscale QOLIE-31 items. CONCLUSION: A colocated psychiatrist demonstrated reduction in psychiatric symptoms of PWEs and PWNESs, improving psychiatric access and streamlining their care. Epileptologists were able to dedicate more time to managing epilepsy as opposed to psychiatric comorbidities. As integrated models of collaborative and colocated care are becoming more widespread, mental health-care providers located in outpatient neurology clinics may benefit both patients and providers.

Improved mapping of interictal epileptiform discharges with EEG-fMRI and voxel-wise functional connectivity analysis.

OBJECTIVE: We describe a novel method to spatially map interictal epileptiform discharges (IEDs) through voxel-wise functional connectivity analysis of the functional magnetic resonance imaging (fMRI) portion of simultaneous electroencephalography (EEG)-fMRI data. This method measures the local synchronicity of fMRI signals associated with IED and, in contrast to conventional methods, does not require modeling of neural activities or hemodynamic response. METHODS: Simultaneous EEG-fMRI was performed on six patients with focal epilepsy. IED events were detected from the EEG data. The fMRI data was subdivided into time segments of 20 s in length, and then reorganized into one set of concatenated time series containing the IED events and many sets without IEDs. Local degree centrality (LDC), a metric of functional connectivity, was computed for each brain voxel to summarize its signal correlations to brain voxels within 14 mm of physical distance. This computation was repeated for each set of concatenated time series, yielding one whole-brain LDC map for time with the IED events and many maps for time without IED. A statistical score was computed for each voxel to detect the voxels with significant LDC value differences associated with IEDs. The fMRI data were also processed separately by conventional methods for comparison. RESULTS: In all six patients, regions with significant LDC increase during IEDs were concordant in location to both simultaneous EEG and the epileptogenic focus determined from separate clinical studies. In contrast, results from the conventional methods were concordant in only three patients. SIGNIFICANCE: We show that for focal epilepsy, voxel-wise functional connectivity analysis of EEG-fMRI data may improve IED localization and EEG concordance compared to the conventional analysis. This new analytic method may improve the robustness of interictal EEG-fMRI as a technique for mapping the epileptogenic focus, and helps study the local synchronization aspect of the epileptic network.

Creation of a human head phantom for testing of electroencephalography equipment and techniques.

We have designed and fabricated an anatomically accurate human head phantom that is capable of generating realistic electric scalp potential patterns. This phantom was developed for performance evaluation of new electroencephalography (EEG) caps, hardware, and measurement techniques that are designed for environments high in electromagnetic and mechanical noise. The phantom was fabricated using conductive composite materials that mimic the electrical and mechanical properties of scalp, skull, and brain. The phantom prototype was calibrated and testing was conducted using a 32-electrode EEG cap. Test results show that the phantom is able to generate diverse scalp potential patterns using a finite number of dipole antennas internal to the phantom. This phantom design could provide a valuable test platform for wearable EEG technology.

Predictive factors of hearing preservation after surgical resection of small vestibular schwannomas.

OBJECTIVE: To identify factors predictive of hearing preservation in patients undergoing resection of small vestibular schwannoma. STUDY DESIGN: A retrospective chart review. SETTING: Tertiary care medical center. PATIENTS: Forty patients with serviceable hearing preoperatively who underwent a potentially hearing sparing procedure for resection of small vestibular schwannoma (extending 1 cm or less into the cerebellopontine angle). INTERVENTION: Resection of vestibular schwannoma via the middle fossa (subtemporal) or retrosigmoid (suboccipital) approach. MAIN OUTCOME MEASURES: Hearing was assessed preoperatively and postoperatively and classified according to the criteria of the American Academy of Otolaryngology-Head and Neck Surgery. Postoperatively, audiograms were unavailable for 5 patients without subjective hearing in the affected ear. These patients are included in the group without hearing preservation. Potential predictive factors of hearing preservation included patient demographics, tumor characteristics, audiometric data, and intraoperative brainstem auditory evoked response (BAER) monitoring. RESULTS: Serviceable hearing was preserved in 23 patients (57.5%). Patient age, sex, preoperative hearing status, tumor size, laterality, extent of internal auditory canal involvement, surgical approach, wave V latency, and wave V amplitude were not predictive of hearing preservation. The presence of wave V on intraoperative BAER was the only significant predictor of hearing preservation (p < 0.019). Serviceable hearing was preserved in 14 patients (77.8%) with wave V present. Of note, serviceable hearing also was preserved in 9 patients (40.9%) without a measurable wave V. CONCLUSION: No preoperative factor was predictive of hearing preservation. The presence of wave V on intraoperative BAER is a significant predictor of hearing preservation. Additionally, absence of wave V does not preclude preservation of serviceable hearing.

Possible axonal regrowth in late recovery from the minimally conscious state.

We used diffusion tensor imaging (DTI) to study 2 patients with traumatic brain injury. The first patient recovered reliable expressive language after 19 years in a minimally conscious state (MCS); the second had remained in MCS for 6 years. Comparison of white matter integrity in the patients and 20 normal subjects using histograms of apparent diffusion constants and diffusion anisotropy identified widespread altered diffusivity and decreased anisotropy in the damaged white matter. These findings remained unchanged over an 18-month interval between 2 studies in the first patient. In addition, in this patient, we identified large, bilateral regions of posterior white matter with significantly increased anisotropy that reduced over 18 months. In contrast, notable increases in anisotropy within the midline cerebellar white matter in the second study correlated with marked clinical improvements in motor functions. This finding was further correlated with an increase in resting metabolism measured by PET in this subregion. Aberrant white matter structures were evident in the second patient's DTI images but were not clinically correlated. We propose that axonal regrowth may underlie these findings and provide a biological mechanism for late recovery. Our results are discussed in the context of recent experimental studies that support this inference.

Neurophysiological correlates of persistent vegetative and minimally conscious states.

The evaluation of patients after severe brain injury is a complex process for the clinician, even with the information provided by a detailed neurological examination. The clinical examination often does not provide sufficient information to fully evaluate these patients due to several factors. Limited and inconsistent motor responses may obscure expression of greater cognitive capacities. More importantly, evaluation of the functional integrity of the cerebral cortical, thalamic and basal ganglia system is poorly indicated by the clinical examination in many patients. Neurophysiological studies provide a complementary set of objective data for evaluating brain-injured patients, as well as predicting and following the course of their recovery. This additional information can be of great importance since vegetative patients may be difficult to distinguish clinically from those in the minimally conscious state. This is important because the latter category of patients may have a significantly better prognosis for recovery in the initial phase of injury. Electrodiagnostic and imaging studies can help the practitioner to determine the degree of preserved and recovering neurological function. In this review we will assess the various neurophysiological studies currently at our disposal to evaluate and follow the clinical course of patients who have suffered severe brain injuries.

Electroencephalographic patterns in unresponsive pediatric patients.

To study the occurrence and incidence of various electroencephalographic patterns, the electroencephalograms of unresponsive pediatric patients admitted to the intensive care unit were analyzed. The interpreters were unaware of the patients' clinical diagnoses. A total of 178 electroencephalographic studies performed on unresponsive patients were analyzed over a period of 3 years. The mean age of the study patients was 7.9 years. Sixty-six patients were less than 1 year old. The following electroencephalographic patterns were observed: 58 patients (33%) manifested electroencephalographic patterns consistent with nonconvulsive status epilepticus. Of the patients with nonconvulsive status epilepticus, 32 patients (18%) had generalized nonconvulsive status epilepticus and 26 patients (14%) manifested partial nonconvulsive status epilepticus. The remaining 120 patients (67%) manifested diffuse cerebral dysfunction, with the majority having severe diffuse cerebral dysfunction. Only 4 patients (2%) had triphasic waves, suggesting a metabolic encephalopathy. Thirty-six percent of the patients under the age of 1 year had electroencephalographic patterns consistent with nonconvulsive status epilepticus. Nonconvulsive status epilepticus is a relatively common electroencephalographic pattern in unresponsive pediatric patients. Metabolic encephalopathy is uncommon in this patient group.